Fig. 2.

Polar cells and stalk cells are specified in Pak mutant paired egg chambers. (A,B) Phalloidin-stained wild-type (A) and Pak mutant ovarioles (B) additionally stained with anti-FasIII to reveal polar cells. Wild-type egg chambers have a pair of polar cells at each pole (arrowheads). Polar cells are specified in Pak mutant ovarioles (arrowheads) but vary in position and number. (C,D) Wild-type (C) and Pak mutant ovarioles (D) stained with anti-βPS integrin to reveal stalk cells. Stalks in wild-type ovarioles are composed of a single row of cells (arrowhead), whereas paired egg chambers in Pak mutants are linked by stalks two rows wide (arrowhead). Scale bars: 50 µm in A for A,B; 25 µm in C for C,D.